Question: Which portion of the Nile runs from where they migrate to the country that borders Egypt to the south?
Context: Document 1: Nile: The Nile (Arabic: النيل‎, written as al-Nīl; pronounced as an-Nīl) is a major north-flowing river in northeastern Africa, and is the longest river in Africa and the disputed longest river in the world (Brazilian government claims that the Amazon River is longer than the Nile). The Nile, which is about 6,650 km (4,130 mi) long, is an "international" river as its drainage basin covers eleven countries, namely, Tanzania, Uganda, Rwanda, Burundi, the Democratic Republic of the Congo, Kenya, Ethiopia, Eritrea, South Sudan, Republic of the Sudan and Egypt. In particular, the Nile is the primary water source of Egypt and Sudan.The river Nile has two major tributaries, the White Nile and Blue Nile. The White Nile is considered to be the headwaters and primary stream of the Nile itself. The Blue Nile, however, is the source of most of the water and silt. The White Nile is longer and rises in the Great Lakes region of central Africa, with the most distant source still undetermined but located in either Rwanda or Burundi. It flows north through Tanzania, Lake Victoria, Uganda and South Sudan.  The Blue Nile begins at Lake Tana in Ethiopia and flows into Sudan from the southeast. The two rivers meet just north of the Sudanese capital of Khartoum.The northern section of the river flows north almost entirely through the Sudanese desert to Egypt, then ends in a large delta and flows into the Mediterranean Sea. Egyptian civilization and Sudanese kingdoms have depended on the river since ancient times. Most of the population and cities of Egypt lie along those parts of the Nile valley north of Aswan, and nearly all the cultural and historical sites of Ancient Egypt are found along river banks.
Document 2: Egypt: Egypt (i/ˈiːdʒɪpt/; Arabic: مِصر‎ Miṣr, Egyptian Arabic: مَصر Maṣr, Coptic: Ⲭⲏⲙⲓ Khemi), officially the Arab Republic of Egypt, is a transcontinental country spanning the northeast corner of Africa and southwest corner of Asia, via a land bridge formed by the Sinai Peninsula. It is the world's only contiguous Eurafrasian nation. Most of Egypt's territory of 1,010,408 square kilometres (390,000 sq mi) lies within the Nile Valley. Egypt is a Mediterranean country. It is bordered by the Gaza Strip and Israel to the northeast, the Gulf of Aqaba to the east, the Red Sea to the east and south, Sudan to the south and Libya to the west.
Document 3: Black people: About 150,000 East African and black people live in Israel, amounting to just over 2% of the nation's population. The vast majority of these, some 120,000, are Beta Israel, most of whom are recent immigrants who came during the 1980s and 1990s from Ethiopia. In addition, Israel is home to over 5,000 members of the African Hebrew Israelites of Jerusalem movement that are descendants of African Americans who emigrated to Israel in the 20th century, and who reside mainly in a distinct neighborhood in the Negev town of Dimona. Unknown numbers of black converts to Judaism reside in Israel, most of them converts from the United Kingdom, Canada, and the United States.
Answer: Blue Nile
Reasoning steps: Where did they migrate from? Answer: Ethiopia.
What country borders Egypt to the south? Answer: Sudan
Which portion of the Nile runs from Ethiopia. to #2 ? Answer: Blue Nile